2026-10-09
829 reads
Aggregates
2026-09-30
1,375 reads
Eager Aggregation in SQL queries
Aggregation is a widely used way to summarize the content of a database. It is usually expressed with GROUP BY clause or just using aggregate functions (like COUNT or SUM). When the database engine executes a query with aggregations, it produces individual rows need to compute the required output and then performs the aggregation as (almost) last step. We discuss in this article how to re-write a query manually so that the order of operations will be different and when it can be beneficial.
2024-01-15
2023-12-01
462 reads
An Overview of PostgreSQL Window Functions
This article looks at Window functions and how they can be used to solve problems in a different way from standard aggregate functions.
2023-02-24
6,233 reads
2020-07-06
766 reads
Handling Aggregations on a Poorly Designed Database
When the database design is not great, you may have to write some creative queries to get what you need.
2020-02-17
3,514 reads
Optimize Your SQL by Reformulating the Spec
As SQL developers, we tend to think of performance tuning in terms of crafting the best table indices, avoiding scalar and table valued functions, and analyzing query plans (among other things). But sometimes going back to the spec and applying some properties of elementary math can be the best way to begin to improve performance of SQL queries which implement mathematical formulas. This article is a case study of how I used this technique to optimize my SQL implementation of the Inverse Simpson Index.
2021-05-07 (first published: 2019-09-12)
5,530 reads
2017-12-14
1,245 reads
2016-09-29
1,418 reads
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Question of the Day
Using CHOOSE()
We have this code that sets some status values and then queries them using the CHOOSE() function in SQL Server 2025.
CREATE TABLE Status
(
StatusID INT,
StatusDescription VARCHAR(20)
);
GO
INSERT dbo.Status
(
StatusID,
StatusDescription
)
VALUES
(0, 'Uncategorized'),
(1, 'Active'),
(2, 'Inactive'),
(3, 'Temp');
GO
SELECT CHOOSE(StatusID, 'Unknown', 'Active', 'Inactive', 'Temporary')
FROM Status;
When the SELECT runs, what is returned? See possible answers